A radar apparatus transmits a radio-frequency (e.g., microwave or millimeter wave) radar transmission signal from a measuring site to the space in every transmission cycle, receive a reflection wave signal reflected from a target, and measure at least one of a distance between the measuring site and the target and a direction of the target.
At present, radar apparatus which transmit a millimeter-wave radar transmission signal (hereinafter referred to as “millimeter-wave radars”) are put in practical use as vehicle-mounted devices such as forward-looking sensors for mainly detecting vehicles (e.g., cars, buses, trucks). Development of radar apparatus to serve as vehicle-mounted millimeter-wave radars which have such a high angular resolution as to resolve distant lanes and enable stable detection of vehicles is desired.
Among related art vehicle-mounted millimeter-wave radars is a radar apparatus which detects a vehicle by transmitting three or more millimeter-wave main beams in such a manner that two adjoining ones of them overlap with each other by what is called sequential roving which is a technique of switching the main beam direction sequentially in a horizontal plane (refer to Patent document 1, for example).
In Japan, at present, for example, high-resolution radar apparatus for detecting a pedestrian or a bicycle are assigned UWB (ultra wideband) bands of 24 GHz and 26 GHz and a 79 GHz frequency band. In view of future diffusion rates of radar systems, it is expected that the 79 GHz frequency band (e.g., 77 to 81 GHz) will be allocated to vehicle-mounted radar apparatus, rather than the UWB bands of 24 GHz and 26 GHz for which use restrictions are set.